It is often desirable to separate constituents in a liquid phase for laboratory analyses, during production, or in the area of bioprocessing. One way to accomplish the separation known in the art is with the use of a liquid chromatograph (LC). A LC has a column with a column-packing material which is commonly referred to as the stationary phase. In reversed phase mode (RPLC), the stationary phase is typically a non-polar material. The eluent, also referred to as the mobile phase, is typically relatively polar and is used to elute the various constituents from the stationary phase. The mobile phase may include, for example, an aqueous solution or a mixture of water and an organic solvent such as an alcohol. Its polarity can be changed by increasing the concentration of the less polar liquid (the alcohol) in the mobile phase, a technique known in the art.
The stationary phase has a solid support material which is typically comprised of synthetic organic polymers and metal oxides such as silica, alumina, titania, zirconia, and hafnia. Silica is the most widely used support for the LC stationary phases. Silane bonding chemistry also allows for a wide variety of stationary phases with different selectivities to be made on a silica support. The most commonly used stationary phases feature a non-polar ligand covalently bound to a porous silica particle through one or more siloxane bonds (Si—O—Si) to render the surface hydrophobic.
A common stationary phase material as is known in the art comprises n-alkyl modified silica RPLC sorbent materials of either monomeric or polymeric linking chemistry as shown in FIGS. 1A and 1B respectively. These stationary materials typically separate the constituents in the mobile phase by mechanisms based on polarity and shape of the constituents. These materials are widely employed for a range of analytical separations, however they may be problematic for the separation of analytes that require a relatively low content of an organic modifier, such as alcohol, in the mobile phase and may not have desired shape separation capabilities.
A process for laboratory use, as is known in the art, comprises injecting a sample solution of constituents into the mobile phase of the assay through an injector port. As the sample solution flows with the mobile phase through the stationary phase, the constituents in the mobile phase solution migrate through the column at varying rates according to the non-covalent interactions of the compounds with the stationary phase. The chemical interactions of the stationary phase and the constituents within the mobile phase determine the rate of migration and separation of the constituents contained in the sample. For example, constituents having stronger interactions with the stationary phase than with the mobile phase elute from the column less quickly, and thus have a longer retention time, and constituents having weaker interactions with the stationary phase than with the mobile phase will elute from the column more quickly, and thus have a shorter retention time.
Columns containing various types of stationary phases are commercially available. However, these stationary phases may not result in the desired separation capabilities of constituents in the mobile phase, especially separation of constituents based on molecular shape recognition. Therefore, what is needed is a stationary phase material having enhanced selectivity, improved molecular recognition and separation of polar and halogenated constituents in highly aqueous solvents.